Improving the energy efficiency of room air conditioners (RACs) will be a critical step toward reducing the energy, peak load, and total lifecycle emissions impacts of RACs while transitioning to low global-warming-potential (GWP) refrigerants under the 2016 Kigali Amendment to the Montreal Protocol. Previous research quantified the energy and climate benefits of leapfrogging to high efficiency in tandem with the transition to low-GWP refrigerants for RACs (Shah et al., 2015) and identified opportunities for initial action to coordinate energy efficiency with refrigerant transition, focusing initially on economies constituting about 65% of the global RAC market (Shah et al., 2017). Previous research by Oak Ridge National Laboratory (ORNL) determined that flammable HC-290 (R-290) and HFC-32 (R-32) are inherently more energy efficient than non-flammable HFC-410A (R-410A). This report describes further research performed to identify the best-performing (i.e., most efficient and low-GWP-refrigerant using) RACs on the market to maximize the lifecycle energy, cost, direct and indirect emissions savings discussed in previous work. By defining and describing current best available technology (BAT), this report can help support market-transformation programs for high-efficiency and low-GWP equipment such as minimum energy performance standards (MEPS), labeling, procurement, performance assurance requirements for imports, and incentive programs. Furthermore, the new strategy of bulk government procurement is proving that high efficiency can be achieved at affordable cost by capturing economies of scale in production, sales, distribution, and installation (Abhyankar et al., 2017; Mathur et al., 2017).